That, and since the Japanese were absolutely unafraid to die, they would have been unlikely to have been intimidated by the Roman's tactics.
Japan for the score.
Romans had scorpios and trebuchets- artillary.
The gladius wasn't developed as a dueling weapon. It was used as part of a system, which included disciplined units fighting behind 3ft shields. And it worked for centuries against Gallic and Germanic tribes swinging much longer swords.
The Japanese were absolutely unafraid afraid to die in WW 2, so we accommodated them. Romans fought and destroyed lots of people who were unafraid to die.